A Bohr model of an atom is a simplified visual representation of invisible atomic structures. You can easily make a model of the complex and sometimes confusing interconnected relations of protons, neutrons and electrons. These models can help students visualize the fundamental principles of the electron orbits of quantum mechanical shells. You can make a simple and low-cost Bohr model of any atom on the Periodic Table of the Elements.
- Periodic Table of the Elements
- 2-inch Styrofoam balls
- 1-inch Styrofoam balls
- Blue acrylic paint
- Red acrylic paint
- Green acrylic paint
- 12-inch bamboo skewers
- White glue
Balls of string, ping-pong balls or any other round objects can be used in place of Styrofoam for the model.
Consult the Periodic Table of the Elements for the atom you wish to model. Look at the electron shell configuration information at the bottom of the atom's data block. For example, a carbon atom shows a shell configuration of "1s2 / 2s2 2p2." This information shows that the first orbit (1s2) has two electrons in it. The second orbit (2s2 2p2) has four electrons in it. The number of the orbit is the first number, the number of electrons is the last number. Another example is a chlorine atom that has a shell configuration of "1s2 / 2s2 2p6 / 3s2 3p5." This shows the first orbit (1s2) with two electrons, the second orbit (2s2 2p6) with eight electrons, and a third orbit (3s2 3p5) with seven electrons.
Determine how many electrons the atom contains. Use the atomic number to find the number of protons, neutrons and electrons the atom contains. This information is available from the Periodic Table of the Elements. For example, a carbon atom has an atomic number of 6. This means the atom has six protons and six electrons. The number of neutrons will be based on the isotope you choose to model; an element can have several isotopes.
Paint 1-inch Styrofoam balls blue to represent electrons. Paint 2-inch Styrofoam balls red to represent protons. Paint 2-inch Styrofoam balls green to represent neutrons. The number of Styrofoam balls you'll need is based on the elemental information from Steps 1 and 2.
Cut a 4-inch section of the bamboo skewers for each electron in the first orbit. Cut an 8-inch section for each electron in the second orbit. Add 4 inches to represent each orbit of the atom. Fasten two skewers together for electrons in orbits greater than the length of a single skewer.
Glue the protons and neutrons together with the white glue. This represents the nucleus of the atom and should be more or less ball-shaped. It doesn't matter in which order you assemble the neutrons and protons.
Attach the electrons to the nucleus using the bamboo skewers from Step 4. Push the Styrofoam balls gently onto the skewers, being careful not to poke the skewer all the way through. Place a small drop of white glue on the end of the skewers to hold the Styrofoam in place. You can place the electrons in flat orbits resembling a wheel or hat, or you can attach them evenly around the nucleus resembling a ball.
Things You'll Need
- "Physics 2nd Edition;" John D. Cutnell and Kenneth W Johnson; 1992
- “Chemistry 4th Edition;" Raymond Chang; 1991
- Jefferson Lab: The Periodic Table of Elements
- black_toy image by Sergey Tokarev from Fotolia.com